Adipocytes are essential regulators of energy balance. In addition to its long recognized role in energy storage, adipoctes function to regulate glucose and lipid metabolism through secretion of various cytokines. Both lipodystrophy and excess adiposity (obesity) can lead to dysregulated glucose and lipid homeostasis resulting in diabetes mellitus and cardiovascular disease. Thus, proper control of adipocyte differentiation and function are essential for proper energy metabolism. While numerous factors controlling the differentiation of committed preadipocytes into mature adipocytes have been identified and characterized, the molecular mechanisms regulating the determination of preadipocytes from mesenchymal precursors have yet to be elucidated. To identify these mechanisms, we will derive novel subclones of Swiss 3T3 fibroblasts with varying potential for adipogenesis which will serve as a model system for preadipocyte determination. Computational analysis of global gene expression profiles of these various clones, followed by extensive functional characterization of identified genes, will identify key regulators controlling preadipocyte formation. The goals of the experiments described in this proposal are to identify the transcriptional mechanisms regulating the commitment of preadipocytes from multipotent progenitors and to derive a set of molecular markers of preadipocytes for the analysis of adipogenesis in vivo. Fat cells are essentials regulators of energy balance and glucose homeostasis. Improper function or development of adipocytes can lead to serious metabolic diseases such as cardiovascular disease and type 2 diabetes. This research will further our understanding of these disorders by delineating the mechanisms controlling the development of the adipocyte lineage.